Electrical switch



July 24, 1962 c. c. CAVALCONTE ELECTRICAL SWITCH Filed sept. e, 1960INVENTOR CHARLES C. CAVALCONTE A ToRA/EY.

United States Patent 3,046,436 ELECTRICAL SWITCH Charles C. Cavalconte,Mineola, N.Y., assigner to Republic Aviation Corporation, nearFarmingdale, N.Y., a corporation of Delaware Filed Sept. 6, 1960, Ser.No. 54,029 Claims. (Cl. 313-146) This invention relates to electricalswitches and, more particularly, to a high current, high voltage switch,i.e., one capable of passing megampere currents at kilovolt potentials.

The present invention contemplates an improved switch design predicatedon a novel operating concept whereby large currents `and voltages arereadily passed with an attendant low erosion and wear to its parts. Atthe same time, the instant high voltage, high current switch is capableof repeated operation with relatively no time delay between successiveswitching operations.

Moreover, the proposed switch ydesign allows for the handling of arelatively wide range of current and voltage values incorporatingadjustable and contoured switch electrodes whereby the length and pathof the arc thereacross during operation may be pre-established to theend .that predictable, conducting characteristics are obtainable. Suchcontrol of the arc finds particular utility in applications wherepulse-shaping of currents, i.e., accurate control of the amplitude andphase of current discharges, is important.

In prior switches capable of passing substantial currents at highvoltages, the designs have been such that reliability of operation isadversely affected with 'the increase in the value of the currents andvoltages handled and the attendant heat generated thereby. Thus, severalseconds elapsed time is required between switching operations in theseearlier `designs and they fail to meet the requirements of many presentday applications because of their repetition rate. For example, switchesare currently available which adequately handle current and volt-agevalues approaching those `herein contemplated, but approximately oneminute of elapsed time is prescribed between each switching operation.Such switches are obviously useless in applications, for example inthermonuclear and magnetohydrodynamic devices, requiring m-any distinctswitching operations a second with currents in the order of, forexample, 0.5 megampere and voltages of 30 kilovolts.

The present invention is, among other things, directed toward a switchthat will meet the requirements set forth above and to this end proposesa switch design predicated on a novel concept by which a greaterrepetition rate is obtained at high current and voltage. Moreover, thisproposed design lends itself to pulse-shaping of currents and `a longlife expectancy of its components.

The switch lherein proposed is founded on a triggered gap principledepending for its operation on the ionization of a gas in the gap andthe creation of magnetic fields which interact to control the currentpath through the switch. More specifically, the instant switch comprisescoaxial conductors insulated lineally and interconnected adjacentcorresponding ends. One of these conductors is interrupted in its lengthrto establish a space or gap preventing a completed circuit. Theterminals of the interrupted conductor ydefini-ng this gap constitutethe switch ICC electrodes which are adapted to operate in a controlledatmosphere, the switch being enclosed in a dielectric, gaslled envelopesealed at low pressure.

iIn the preferred form of the invention, a selected, constant potentialis applied to the coaxial conductors, such potential being less thanthat required to bridge or arc lthe gap between the switch electrodes.The gap is normally maintained at a constant voltage breakdown value byadjustment of the space between the electrodes and the ygas or inertiluid pressure therein. However, electrical means, including means tocontrol its operation, is provided to ionize the gas in the gap whendesired to support a current and thereby complete the circuit.

In any case, the coaxial design is employed to produce when operativesubstantially coextensive currents of opposite directions, each with anindividual, associated magnetic field. The interaction of these magneticiields in the area of the gap produces a magnetic pressure on thecurrent across the gap resulting in a phenomenon known as inverse pinch,i.e., lateral movement of the currents outwardly from the conductors,rst assuming an arc or bow in the current formation lacross the gapwhich eventually ruptures to break the circuit.

'Phe iadjacent surfaces of the switch electrodes are contoured inaccordance with the particular application to establish a predeterminedcurrent formation across the gap and movement thereof outwardly rat aprescribed rate whereby its phase and amplitude are made to correspondto the requirements ofthe associated load. Additional controlrefinements are accomplished by means of and through adjustment means tolocate the electrodes with reference to each other and thereby determinethe length of the gap. Thus, by relating the plasma dynamics asdetermined by the particular gas employed tothe resulting magneticforces established by the electrode shape and spacing, ythe conductingcharacteristics of the high current, high voltage switch can be tailoredto a given application'.

With the above and other objects in view, as will be apparent, thisinvention consists in the construction, combination and arrangement ofparts -all as hereinafter more fully described, claimed and illustratedin the raccompanying drawings, wherein:

FIG. l is a transverse section taken through a switch constructed inaccordance with the teachings of this invention to show a preferredembodiment thereof, including associated electrical control means `forits operation, connected in an illustrative high voltage, highcurrentcarrying circuit;

FIG. 2 is a schematic exploded view of the inner and outer conductors ofthe coaxial design illustrating the current path of each and forpurposes of analysis the individual magnetic fields established thereby;and

FIG. 3 is a ldiagram symbolizing the individual current direction ofeach conductor Iand Ithe summation forces of the resulting magneticiield directions illustrated in FIG. 2.

With particular reference to the drawings, 10 designates the presentswitch 'assembly adapted to be connected to, and control the currentpassing through, a circuit 11 connecting a power supply 12 to a loadY 13requiring a large current at high voltage. A battery of capacitors 14 isoperatively connected to the power supply 12, being charged vthereby andupon operation off the switch to effect large current dischargessatisfying the requirements of the load 13.

The switch assembly 10 comprises a pair of coaxial conductors and 16,the inner conductor 15 constituting a rod the outer end of which isadapted to form one terminal by which the switch 10 is connected to thepower side of the circuit 11. The corresponding end of the outerconductor 16 is adapted to form the other terminal for connection of theswitch y10 to the load side of the circuit 11. Medially of its lengththe outer conductor 16 is interrupted, creating a gap 19 with theadjacent ends of the conductor that define this gap constituting a pairof coacting electrodes 17 and 18.

The inner conductor 15 is electrically connected to the electrode 17,for example, being press fitted in a recess provided in the centerthereof and electrically insulated from the electrode 18 by a wrapper 20of dielectric material preferably one having good heat resistanceproperties which overlies and encloses that portion of the innerconductor 15 adjacent the electrode 18 and across the L gap 19.

The electrodes 17 and 18 are provided with coacting adjacent surfaces17a and 18a, respectively, that are generally convex to locate theminimal distance point adjacent the axial center of the gap 19. Adjacentits center, surface 17a is additionally formed with a recess 17b adaptedto surround and thereby separate the rod 15 and insulating wrapper 20from the minimal distant point between the surfaces 17a and 18a. Thus,when a discharge of current is effected, by means to be described,across the electrodes 17 and 18, this current and accompanying heat isdirected away from the wrapper 20 to prevent the deterioration thereof.

The end of the electrode 18 remote from the gap 19 terminates in athreaded concentric projection 21 adapted to receive a coacting nut 22,The nut 22 is pierced centrally by a hole through which the rod 15passes and to which it is secured against lineal movement by suitablemeans such as a lock-ring and seal 23 of flexible material adapted to-be compressed against the end surface of the projection 21 and thesurface of the wrapper 20 upon tightening of the nut 22. Thus, theposition of the -rod 15 may be adjusted in the electrode 18 andmaintained in the adjusted position, establishing the relative positionsof the electrode surfaces 17a and 18a and the length of the gap 19accordingly.

Adjacent the projection 21 the electrode 18 is provided with a lateralflange 24, the peripheral surface of which engages and is suitablysecured, as by press fit, to the inner marginal surface of an envelopeor casing 2S which encloses and houses the coaxial conductors 15 and 16.A removable and replaceable cover plate a closes this end of theenvelope 25. The length of the ange 24 is such that the interior wallsof the casing 25 are disposed in spaced relation to the conductors 15and 16 and thereby Acreate a chamber 26 in which the conductors areconcentrically mounted. The envelope 25 including cover 25a isfabricated of dielectric material and is provided with a port adapted toreceive and connect an inlet duct and check valve 27 by `means of whichan inert fluid such as nitrogen, argon, etc., is admitted into and fillsthe chamber 26 where it is maintained at a selected low pressure.

A pair of opposed conducting probes 28 are mounted within the envelope25 and terminate inwardly thereof in ends disposed within the gap 19 inspaced relation. The outer end of each probe 28 is secured in a recessedbearing of dielectric material, preferably one having good heatresistance properties, forming a localized area of the wall of theenvelope 25. The bearings 30 also serve as seals to prevent uid leakagefrom the chamber 26. O-rings 29 may be employed if desired for the samepurpose adjacent each opening in the envelope 25 through which the duct27 and conductors 15 and 16 are adapted to pass.

The outer end of each probe 28 is appropriately connected by a conductor31 to the opposite ends of the high voltage side of a step-uptransformer 32. The low voltage side of the transformer 32 is connectedat its opposed ends in a circuit 33 comprising a power source such as,for example, battery 34 and a push button on-off switch 35.

The operation of the assembly as above described is as follows:

Constant power is available from the supply 12 and the capacitors 14 tothe inner conductor 15 and electrode 17 of the outer conductor 16.However, the rod 15 is ad justed lineally and secured in the adjustedposition by lock-nut 22 to establish the dimensions of gap 19 wherebythe circuit 11 through the outer conductor 16 to the load `13 isinterrupted. When it is desired to complete this circuit, switch 35 isclosed momentarily whereby a -relatively small current from battery 34passes through the circuit 33 including the primary of the transformer32. When the primary is thus energized, a sufficient voltage is inducedin the secondary of transformer 32 to produce a current arc across theprobes 28. The gases in the gap 19 are thereby ionized, causing abreakdown of this gap whereby the voltage applied on electrode 17 of theouter conductor 16 results in a current across the gap, completr ing thecircuit to the load 13.

Referring momentarily to FIG. 2, it is seen that a current passingthrough the inner conductor 15 takes a path in a direction I andestablishes an associated magnetic field B. On the other hand, a currentpassing between the electrodes 17 and 18 has a direction I' and anassociated magnetic field B. Since the current density appearing on theinner conductor 15 is greater than that of the outer conductor 16, themagnetic field B' is of less magnitude than the field B. Moreover, thesefields B and f B due to the current direction in the conductors 15 and16 are of opposite direction (FIG. 3). The natural interaction of theseopposed fields results in a radially outward magnetic pressure thatforces the current in the gap 19 from an initial position substantiallyparallel to the axis of the conductors 15 and 16 to an arcuate or bowedposition.

Thus, the current l' passing between the surfaces 17a and 17b 0f theelectrodes 17 and 18 of the outer conductor 16 is not concentrated inany loaclized area but distributed rapidly over the entire area of theelectrode surfaces by successive lines of current moving from a point orpoints adjacent the axial center of the gap 19 outwardly. Normalelectrode erosion is thereby held to a minimum during operation of thegap switch.

In addition, the frequency and amplitude of the current discharge acrossgap 19 and to the load 13 as determined by the current formation andbowing as described may be controlled by preselecting the areas andcontours of the electrode surfaces which define the gap 19. Additionalcontrol is obtained by precise adjustment of the length of the gap 19,i.e., the spacing between the surfaces 17a and 18a, by locating theposition of the electrode 17 relative to electrode 18 through means 22.The size of the envelope 25 is such that the width of the chamber 26permits total bowing of the current across gap 19 and ultimate ruptureof the current lines prior to contact with the walls of the envelope 25.It may, therefore, be said that the current discharge across theelectrodes is unconfined and controlled solely by the magnetic pressureor blow out effect produced by interaction of the current fields asdescribed.

From repeated operations of switches constructed as hereinabovedescribed, it has been learned that current discharges across theelectrodes 17 and 18 have had substantially no deleterious effect uponthe probes 28. Presumably, this is explained by the fact that suchdischarges are of short duration, i.e., less than microseconds.Moreover, no backup effect has been experienced in the circuits 31 and33 as a result of the current discharges across the electrodes 17 and18, since the circuit 31 has a high impedance relative to the circuit11.

What is claimed is:

l. An electrical switch comprising coaxial conductors insulated lineallyfrom each other and electrically connected adjacent one of their endsand electrically unconnected adjacent their other ends, each beingindividually connected at said other ends to opposite sides of acircuit, a gap in the length of one of the conductors interruptingcurrent continuity, and control means operative to bridge said gapwhereby current continuity is established through the conductors.

2. A switch as recited in claim 1 including means to adjust said gap.

3. An electrical switch comprising a pair of coaxial conductorsinsulated lineally one from the other and electrically connected one tothe other adjacent corresponding ends, individual -terminals adjacentthe other corresponding ends of said conductors, a lead connecting eachof said terminals to a power supply and load, respectively, a gap in thelength of one of the conductors interrupting current continuity, andmeans operative to bridge said gap whereby said power supply iselectrically connected to said load.

4. An electrical switch comprising a pair of coaxial, substantiallycoextensive conductors insulated one from the other and electricallyconnected adjacent corresponding ends, a gap in the length of One of theconductors interrupting current continuity, means maintaining inertfluid in said gap at low pressure, and means operative on said uid toionize it whereby current continuity is established through saidconductors.

5. A switch comprising a pair of coaxial conductors electricallyconnected adjacent one of their ends and insulated lineally, terminalsat the other ends of said conductors, one said terminal ybeing connectedto a power supply and the other said terminal being connected to a load,a gap in the length of one of the conductors interrupting currentcontinuity, current discharging means operative in said gap to ionizeiiuid therein, and control means for the operation of said currentdischarging means whereby current continuity is established through theconductors from the power supply to the load.

6. A switch comprising a pair of coaxial conductors electricallyinterconnected adjacent corresponding ends and insulated one from theother substantially throughout their length, a source of applied voltageconnected to the free end of one of said conductors, a load connected tothe free end of the other of said conductors, a gap in the length of oneof the conductors interrupting current continuity therethrough, meansmaintaining inert fluid in said gap at pressure below that required tosupport a current across the gap, and means operative on said iiuid toionize it whereby said applied voltage results in a current dischargeacross said gap to said lo-ad.

7. An electrical switch comprising a pair of electrodes, a gap betweenadjacent ends of said electrodes, means producing a discharge currentbetween said electrode ends and across said gap outwardly of the axialcenterline thereof, and a current of opposite direction to saiddischarge current adjacent said centerline, said current establishing amagnetic eld at right angles to said discharge current forcing itradially outward of the gap.

8. An electrical switch comprising a pair of axially aligned electrodes,a gap 'between said electrodes, lmeans producing a discharge current andan associated magnetic eld across said electrodes outwardly of theircenterline, and a current of opposite direction to said dischargecurrent adjacent said centerline establishing a magnetic iield inopposition to the iirst magnetic eld whereby said current discharge isforced radially outward orf the gap and eventually interrupted.

9. An electrical switch comprising coaxial conductors interconnected atone of their ends, a pair of electrodes in the length of one of saidconductors, a gap between said electrodes, a power supply and a load,respectively, connected to the other ends of said conductors, and meansoperative to discharge said power supply producing a discharge currentacross said electrodes completing la circuit to said load wherebymagnetic fields are created in said gap to force the current therein ina radial `direction and eventually breaking said circuit.

10. An electrical switch comprising a gas-filled envelope havingindividual, insulated terminals, a pair of insulated coaxial conductorswithin said envelope connected at one of their ends tto said terminals,respectively, means establishing opposite current directions through thecon; ductors, means establishing a gap in one of said currentdirections, a source of applied voltage constantly connected to one ofsaid terminals and normaly inoperative to pass a current across saidgap, electrical means operative in the gap to ionize gas therein andsupport a current, and a control to render said electrical means'operative whereby current passes bet-Ween said terminals.

11. An electrical switch comprising `a duid-tight envelope, a pair ofcoaxial conductrs interconnected at corresponding ends and disposedwithin said envelope, a gap in the length of `one of -said conductorsnorm-aly operative to interrupt current continuity therethrough, meansconnected to and forming a part of the envelope for iilling andmaintaining it including said gap with gas at a selected pressure, andcontrol means mounted in and opera-ble exter-nally of the envelope toionize gas thereiniwhereby current Icontinuity is established 'acrosssaid gap and through the conductors.

12. An electrical switch comp-rising a pair of coaxial conductorselectrically interconnected adjacent one of their ends and insulatedlineally one Ifrom the other, a gap i-n the length of the outer of saidconductors dened by adjacent, generally convex surfaces, meansconstantly connecting a source of electric power -to the free end of theinner conductor, means connecting a load to the free end of the outerconductor, the dimensions of the ygap being such as to normallyinterrupt current continuity -front the source to the load and establisha voltage diiferential across the gap, means to maintain a gas in thegap, and electrical means operative to ionize -said gas therebyestablishing current continuity yacross the gap.

13. An electrical switch comprising la lfluid-tight envelope, a pair ofcoaxial conductors mounted within said envelope, the inner of saidconductors including a central conductive rod disposed within andprojecting externally from the envelope and connected to a source ofelectrical power, the end of said rod with-in the envelope beingelectrically connected to the corresponding end of the outer conductor,a pair of spaced coacting electrode elements in the length of the outerconductor overlying and surrounding the rod and creating a gap,electrical connection means between the outer conductor and a load, andmeans operable externally of the envelope to ionize fluid in the gapaforesaid whereby current continuity is established across the gapbetween the electrode elements aforesaid.

14. An electrical switch comprising a uid-tight envelope, a pair ofinsulated, coaxial conductors mounted within said envelope, the inner ofsaid conductors cornprising a lineally adjustable, conductive roddisposed within and projecting externally from the envelope to connect asource of electrical power, the end of said rod within the envelopebeing electrically connected to the outer conductor, the outer of saidconductors including a pair of spaced, axially aligned, concentricelectrode elements establishing a variable gap therebetween asdetermined by the adjusted position of the rod, an insulator between therod and said gap, an electrical connection between said outer conductorand a load, an inert gas in the gap, and means to ionize said gaswhereby current from the source is discharged across said gap andapplied to the load.

15. An electrical switch comprising a fluid-tight envelope, a pair ofinsulated coaxial conductors mounted within said envelope, the inner ofsaid conductors comprising a central conductive rod disposed within andprojecting externally from the envelope to connect a source ofelectrical power, the end of said rod within the envelope beingelectrically connected to the outer conductor, a pair of coactingelectrode elements in the length of said outer conductor one connectedto the rod and the other to the envelope in spaced relation to the rstto create a gap, adjustment means to regulate the length of the roddisposed within the envelope whereby the length of said gap is`established and current continuity through the conductors isinterrupted, electrical-connecting means between said electrode elementand a load, and means operable externally of -the envelope to ionize uidin the gap aforesaid whereby current continuity is established acrossthe gap between the electrode elements whereby electrical power from thesource is applied to the load.

References Cited in the fiile of this patent UNITED STATES PATENTS

